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Diseased ‘Indian’ Mint

rorymeuprorymeup Posts: 4
edited September 2019 in Problem solving

Complete beginner here, after a little help fighting what seems a losing battle. 

Ive just started herb gardening, only for one disease to rip through two dozen varieties of mint, oregano, and marjoram. After some googling and guesswork I identified it as mint rot (I had been showering them with water, and they were crowded). I cut most back to almost nothing, sprayed with a fungicide, and brought them inside. Some died, but lost are now doing well. (Most fora say to dispose of infected plants, but as it has seemingly infected all of my plants, there’s little to lose in attempting a rescue.)

Not having much luck, I then noticed almost all of my other (non-mint; mainly rosemary, thyme, and other hard herbs) plants doing poorly with white blotches on leaves. I’m still not quite sure what the problem is, but my best guess has been spider mite, with a similar resolution to above but a different spray. 

...anyway, my Indian mint was doing really well trailing down the side of my shed. Until I noticed a white mildew. I removed those leaves (and some stems) but things have continued downhill. It now seems a mix of things: yellowing areas, then black spots, that see leaves ultimately turn brown and fall off (many, but not all, have some white mildew on the underside) [as first picture]; others have ‘trails’ of very small white dots [second pixture]. 

I’m at a complete loss. The mint is alternated with creeping red thyme and trailing rosemary (which again looks to have spider mite) so I’d be quite sad to lose the lot, but am increasingly resigned to starting again. Any help appreciated!




  • BorderlineBorderline Posts: 4,700
    It's very difficult to advise without some photos. The Indian Mint might not do so well if you grow them touching other plants or the soil. Might be an issue with air flow like you say and it's showing signs of a fungal infection.

    Most treatments don't tend to work, especially once you have the issue. With most plants, it's more about giving your plants what they need and like. Excess watering or watering into the foliage over long periods will cause spread of fungal infections too. 

    Rosemary and Thyme normally require lots of sun and very free draining soil. They do not mind dry conditions. Watering deep around the base once a week is better than watering often. Spider mites, you would normally see webbing if you get closer. 
  • Thanks Borderline. I really thought I’d added photos in my post, but must have added them wrongly somehow. Has it worked this time?
  • BorderlineBorderline Posts: 4,700
    edited September 2019
    Those pictures have shown up, but not certain about spider mites. Normally you would see webbing around your plants. It could be that or even Thrips.

    The top photos look like a fungal infection which as mentioned before, you need to look at the growing conditions and watering. Water at the base and try to not let the foliage touch the ground or other plants. Watering onto the foliage can spread the infection.

    Sometimes a combination of local weather conditions make it more susceptible to thrips and spider mite. Consistent watering, and never allowing the plants to go through excess dry periods tend keeps them at bay.

    Your description of plants sounds like they are planted too close together and Rosemary, Thyme etc need free draining dry soil whilst your mint prefers more moist, but free draining soil. Very different conditions. Might be best to keep them in very different areas so when watering, they do not affect neighbouring plants that require different water and sun levels.
  • Thanks. Hadn’t thought that they might like different conditions so will have to give that some thought (they’re planted in a feed trough on top of the shed, in a 3:1 mix of compost and vermiculite).

    What next though? I would like to have trailing mint down that side so am happy to repot the thyme and rosemary, but would you try to preserve with the current mint (paying more attention to air circulation and watering) or give up and start again next year?
  • BorderlineBorderline Posts: 4,700
    I’m not familiar with this plant but if you cut it right back, give it a good water and top dress more compost it may recover. With its trailing habit might be better to grow it in a container.
  • It is essentially in one long container. But I’ll get another, so I’ve one for mint and one for rosemary and thyme. 

    Last question, I promise (I do appreciate you help, this has got me quite down!)

    The photo below shows (l-r) rosemary, ‘mojito’ mint, and lavender. All have a white speckling but look otherwise healthy. Same on my silver thyme, and sages. I had thought it was another fungus but now wonder if it’s a sage or Ligurian leaf hopper. What would your guess be? ...any sure fire way to tell? 

  • BorderlineBorderline Posts: 4,700
    edited September 2019
    Looking at those images, if you can't see any tiny small creamy/white small bugs about, it’s most likely Spider Mites. Sometimes, if you place a piece of white paper underneath the plant, then give the leaves a bit of a shake, you can see small specks drop down, otherwise impossible to see with the naked eye.

    If it is the case, you need to regularly spray the plant leaves with water to knock off the pests, and also keeping the plants cool. They thrive in dry and hot overcrowded environments. You will need to keep doing this whilst it is still warm. Because you are growing in one long container, it's most likely spread. I do recommend for now, keep them separate.
  • raisingirlraisingirl Posts: 6,896
    I've had a look in a few of my herb books - I've got quite a few - and can't see anything like it. I would guess it's a general issue of the plants just not being happy and falling prey to any passing pest. I'd recommend getting yourself a good book on herb growing (this would be my pic but there are lots to chose from ) and have a careful read of the soil mixes and cultivation conditions for your herbs grown in containers. They don't, for example, do well in standard multi-purpose compost.

    I think 'Indian mint' is actually a type of savory - satureja - which generally likes sunnier and drier conditions than a mint - mentha. 

    Herbs are generally pretty tough so a bit of repotting and cutting back is likely to rejuvenate them from most problems. Rosemary may be the exception.
    “It's still magic even if you know how it's done.” 
  • Youve been given good advice 😊 one more thing to remember is that at this time of year mint will be beginning to die down for the winter ... you can cut it hard back in the autumn or wait until the spring and then cut it back close to the base when you see the new shoots beginning to appear from the root area. 

    Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.

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